Highly Sensitive Planar Anapole Microresonators for Electron Paramagnetic Resonance Spectroscopy of Submicroliter/Submicromolar Samples

摘要：电子顺磁共振(EPR)谱可以提供有关 生理相关条件下生物大分子的结构和动力学。它本身就很高 对于一些质量有限的样品--例如膜蛋白--灵敏度仍然不够 是出了名的难以表达、提纯和结晶。该项目旨在降低对 电感检测EPR谱在室温下的检测，使低产率 生物大分子样品可以在生理相关条件下进行研究。要做到这一点 目标，我们将使用一种新的谐振器设计，将平面微谐振器和 传统的腔体谐振器。我们新颖的平面反极点微谐振器设计提供了 纳升活性体积与高品质因数相结合，预计可提高两个 在室温下的灵敏度为数量级。我们的首要目标是设计和制造 工作在9 GHz和34 GHz的微谐振器。首先，我们将进行有限元模拟 耦合到波导的谐振器的场分布和反射系数。基于这些 结果，我们将优化器件的几何和尺寸，以获得纳升磁场热点 和高品质因素。我们将在NIST纳米加工中心制造这些优化的谐振器 设施。接下来，我们将对微谐振器进行表征，并将其集成到商用9 GHz和 国产34 GHz EPR光谱仪。我们的第二个目标是证明这些谐振器的可行性。 用于结构生物学EPR波谱实验。要做到这一点，我们首先要设计和制造 能够在磁热点体积中定位纳升样品体积的微流控器件 微谐振器。为了验证设备性能，我们将使用一系列自旋标记的浓度 多肽。最后，为了演示对生物大分子样本的适用性，我们将研究G蛋白 偶联受体黑素。如果成功实施，这种谐振器设计将实现 EPR光谱具有前所未有的灵敏度，扩大了其对低产作物的适用性 目前对其结构知之甚少的生物大分子样本。

Abstract: Electron paramagnetic resonance (EPR) spectroscopy can provide information about the structure and dynamics of biomacromolecules in physiologically relevant conditions. Its inherently high sensitivity is still inadequate for some mass-limited samples -- for example, membrane proteins -- which are notoriously difficult to express, purify, and crystallize. This project aims to decrease the limit of detection for inductive-detection EPR spectroscopy at room temperature, so that low-yield biomacromolecular samples can be studied under physiologically relevant conditions. To achieve this objective, we will use a novel resonator design that bridges the gap between planar microresonators and conventional cavity resonators. Our novel planar inverse anapole microresonator design provides nanoliter active volumes combined with high quality factors, providing a projected improvement of two orders of magnitude in sensitivity at room temperature. Our first aim is to design and fabricate microresonators for operation at 9 GHz and 34 GHz. First, we will carry out finite element simulations of the field distributions and reflection coefficients for resonators coupled to waveguides. Based on these results, we will optimize the device geometry and dimensions to obtain nanoliter magnetic-field hotspots and high quality-factors. We will fabricate these optimized resonators at the NIST Nanofabrication facility. Next, we will characterize the microresonators and integrate them into a commercial 9 GHz and home-built 34 GHz EPR spectrometer. Our second aim is to demonstrate the viability of these resonators for structural biology EPR spectroscopy experiments. To do this, we will first design and fabricate microfluidic devices capable of localizing nanoliter sample volumes in the magnetic hotspot volume of the microresonator. To validate the device performance, we will use a concentration series of spin-labeled peptides. Finally, to demonstrate applicability to a biomacromolecular sample, we will study the Gprotein coupled receptor melanopsin. If successfully implemented, this resonator design will achieve an unprecedented sensitivity for EPR spectroscopy, broadening its applicability to low-yield biomacromolecular samples whose structures are currently poorly understood.